Recently, for the safety of pedestrians, a vehicle pop up hood apparatus has been developed in which, when a vehicle collides with a collision body such as a pedestrian, a rear end portion of a hood is raised up and the collision body is received by the hood, and a shock of the collision body is alleviated by the hood. For example, in the vehicle pop up hood apparatus disclosed in cited document 1, a pair of left and right hood hinges are provided at both sides of a rear end portion of a hood, and when a collision occurs with a collision body, actuators provided near the hood hinges operate and a hood side link of each hood hinge is raised upwards by a raising rod.
However, when only the rear end portion of the above hood is raised, if a collision body collides near a position at which the hood is raised, since the raising rod pushes this area, a large reaction load force may act upon the collision body. Therefore, it is desirable for a separate energy absorbing mechanism to be added to the vehicle pop up hood apparatus, so that in cases such as the above a predetermined amount of energy can be absorbed with a predetermined reaction load force or less.
In cited document 2, a technique is disclosed in which an energy absorbing mechanism is added to an actuator that operates a vehicle safety apparatus at a time of collision. In brief, when a load in an axial direction equal to or greater than a predetermined value is input to a distal end portion of a piston rod, a plastically deformable portion provided at the piston rod is crushed, and thereby the piston rod contracts within (moves relative to) a cylinder. Thus, it is conceivable that by using the actuator of cited document 2 with the vehicle pop up hood apparatus of cited document 1, the above needs might be addressed.    Cited document 1: Japanese Patent Application Laid-Open (JP-A) No. 2005-225392    Cited document 2: Japanese Patent Application Laid-Open (JP-A) No. 2004-308785